The present invention relates to dispensing devices such as syringes and the like, and, more particularly to such a dispenser in which there is provided means for evacuating air from the cavity after product has been placed therein and the piston inserted thereabove.
As is well known, syringes and like dispensers in which a plunger or push rod is pushed to dispense the contents are widely used for many applications from medicine to industrial activities. Generally, such dispensers will have a barrel or other container providing the cavity, a dispensing opening at one end, and the other end is open end for insertion of the product thereinto. Because it is desirable to avoid leakage around the piston as it is moved forward to dispense the material, air is trapped below the piston as it is pushed into the cavity above the material.
In order to eliminate the air from the cavity, various procedures have been utilized including a vent in the piston which is subsequently closed. If the vent is not completely closed, there are obvious problems when the syringe is put into use. If the air is not completely evacuated, it may interfere with the operation of the dispenser by causing disruptions in a smooth flow.
Accordingly, it is an object of the present invention to provide a novel and improved dispensing assembly in which air may be readily removed from the cavity after the cavity has been filled with the desired product and the piston placed therein.
It is also an object to provide such a dispenser which can be fabricated readily and economically.
Another object is to provide such a dispenser in which the sealing elements and the venting element can be overmolded on the basic piston.